Field
Embodiments of the invention relate to electronic circuits, and more particularly, to voltage variable attenuators.
Description of the Related Technology
A variable gain passive attenuator can be used in RF (radio frequency) applications where variable signals require continuous adjustment. An attenuation level, relating an output power level to an input power level, can be adjusted by a control signal or control voltage within an analog feedback loop. The variable gain passive attenuator can further be adjusted to have a characteristic impedance matched to an input and output load.
In one application a variable gain passive attenuator is used in a transceiver to adjust the signal strength of a power amplifier input signal. A sample of the transmitted signal strength can be used to vary the gain of the attenuator, and in this way the power amplifier is protected from input signal overload.
In another application a variable gain passive attenuator is used in front of a LNA (low noise amplifier) to keep the total gain constant. Used within a feedback loop in the forward path of the LNA, the variable gain passive attenuator can be used for gain leveling and for impedance matching.